Rift Quest:The Means of the Endless  

1. Acquire the Quest from Sylver in Meridian (College of Planar Studies) before heading to Smith's Haven.
2. Acquire an Attunement Shard at Smith's Haven. If you head north from Denegar's Stand through the main gate into Smith's Haven, the first house on the left will have a Endless Nightbringer on the second floor.
3. Use the shard at three towers around the map. The towers are located in:
• Savage Hill' to the South (across road from Warden's Rise) 6887, 5944
• a bit northeast of Smith's Haven 7250, 5129 (you can refer to the X's on the map to the right to help find them).
• North of Meridian at the back of Falsehood Slope

You can refer to the X's on the map to the right to help find them.

Be careful, as when the towers drop at 75%, 50% and 25% health, they will spawn tough adds (3 to 6 mobs of 3k health), and at 25% a mini-boss will spawn.

There IS an easier way. Two Saboteurs can charge it up to full, blow it at same time, send in their pets, charge it back up and blow the anchor, then die, respawn, run back, resurrect and loot the box.

Also, the mobs de-spawn about a minute or so after killing the tower. So once you burn down the tower, wait a bit and pick up the box.